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From 3c74f736c657d007770fe866842b08d0a74772ca Mon Sep 17 00:00:00 2001
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From: Mark Reynolds <mreynolds@redhat.com>
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Date: Wed, 9 Dec 2020 15:21:11 -0500
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Subject: [PATCH 6/6] Issue 4414 - disk monitoring - prevent division by zero
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crash
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Bug Description: If a disk mount has zero total space or zero used
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space then a division by zero can occur and the
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server will crash.
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It has also been observed that sometimes a system
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can return the wrong disk entirely, and when that
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happens the incorrect disk also has zero available
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space which triggers the disk monitioring thread to
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immediately shut the server down.
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Fix Description: Check the total and used space for zero and do not
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divide, just ignore it. As a preemptive measure
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ignore disks from /dev, /proc, /sys (except /dev/shm).
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Yes it's a bit hacky, but the true underlying cause
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is not known yet. So better to be safe than sorry.
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Relates: https://github.com/389ds/389-ds-base/issues/4414
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Reviewed by: firstyear(Thanks!)
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---
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ldap/servers/slapd/daemon.c | 22 +++++++++++++++++++++-
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ldap/servers/slapd/monitor.c | 13 +++++--------
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2 files changed, 26 insertions(+), 9 deletions(-)
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diff --git a/ldap/servers/slapd/daemon.c b/ldap/servers/slapd/daemon.c
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index 691f77570..bfd965263 100644
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--- a/ldap/servers/slapd/daemon.c
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+++ b/ldap/servers/slapd/daemon.c
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@@ -221,7 +221,27 @@ disk_mon_get_mount_point(char *dir)
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}
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if (s.st_dev == dev_id) {
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endmntent(fp);
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- return (slapi_ch_strdup(mnt->mnt_dir));
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+
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+ if ((strncmp(mnt->mnt_dir, "/dev", 4) == 0 && strncmp(mnt->mnt_dir, "/dev/shm", 8) != 0) ||
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+ strncmp(mnt->mnt_dir, "/proc", 4) == 0 ||
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+ strncmp(mnt->mnt_dir, "/sys", 4) == 0)
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+ {
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+ /*
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+ * Ignore "mount directories" starting with /dev (except
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+ * /dev/shm), /proc, /sys For some reason these mounts are
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+ * occasionally/incorrectly returned. Only seen this at a
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+ * customer site once. When it happens it causes disk
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+ * monitoring to think the server has 0 disk space left, and
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+ * it abruptly/unexpectedly shuts the server down. At this
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+ * point it looks like a bug in stat(), setmntent(), or
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+ * getmntent(), but there is no way to prove that since there
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+ * is no way to reproduce the original issue. For now just
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+ * return NULL to be safe.
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+ */
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+ return NULL;
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+ } else {
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+ return (slapi_ch_strdup(mnt->mnt_dir));
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+ }
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}
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}
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endmntent(fp);
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diff --git a/ldap/servers/slapd/monitor.c b/ldap/servers/slapd/monitor.c
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index 562721bed..65f082986 100644
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--- a/ldap/servers/slapd/monitor.c
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+++ b/ldap/servers/slapd/monitor.c
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@@ -131,7 +131,6 @@ monitor_disk_info (Slapi_PBlock *pb __attribute__((unused)),
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{
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int32_t rc = LDAP_SUCCESS;
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char **dirs = NULL;
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- char buf[BUFSIZ];
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struct berval val;
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struct berval *vals[2];
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uint64_t total_space;
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@@ -143,15 +142,13 @@ monitor_disk_info (Slapi_PBlock *pb __attribute__((unused)),
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disk_mon_get_dirs(&dirs);
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- for (uint16_t i = 0; dirs && dirs[i]; i++) {
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+ for (size_t i = 0; dirs && dirs[i]; i++) {
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+ char buf[BUFSIZ] = {0};
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rc = disk_get_info(dirs[i], &total_space, &avail_space, &used_space);
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- if (rc) {
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- slapi_log_err(SLAPI_LOG_WARNING, "monitor_disk_info",
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- "Unable to get 'cn=disk space,cn=monitor' stats for %s\n", dirs[i]);
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- } else {
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+ if (rc == 0 && total_space > 0 && used_space > 0) {
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val.bv_len = snprintf(buf, sizeof(buf),
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- "partition=\"%s\" size=\"%" PRIu64 "\" used=\"%" PRIu64 "\" available=\"%" PRIu64 "\" use%%=\"%" PRIu64 "\"",
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- dirs[i], total_space, used_space, avail_space, used_space * 100 / total_space);
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+ "partition=\"%s\" size=\"%" PRIu64 "\" used=\"%" PRIu64 "\" available=\"%" PRIu64 "\" use%%=\"%" PRIu64 "\"",
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+ dirs[i], total_space, used_space, avail_space, used_space * 100 / total_space);
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val.bv_val = buf;
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attrlist_merge(&e->e_attrs, "dsDisk", vals);
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}
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--
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2.26.2
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